1. Field of the Invention
The present invention relates to a one-way clutch and more particularly to a one-way clutch adapted to be disposed in parallel with a hydraulic friction element which is incorporated in an automatic transmission or the like.
2. Description of the Related Art
The specification of U.S. Pat. No. 5,918,715 discloses as a conventional one-way clutch a plate type one-way clutch comprising a pair of first and second plates facing each other in an axial direction thereof. Pocket portions are concavely provided in an axially internal surface of the first plate, while notched portions are concavely provided in an axially internal surface of the second plate, and pawls are tiltably mounted in the pocket portions. With this structure, when the first plate rotates in one direction relative to the second plate, the pawls are allowed to sink into the pocket portions to thereby permit the first plate to rotate in the one direction relative to the second plate, whereas the relative rotation of the first plate to the second plate in the other direction is prevented by engagement of the pawls with the notched portions.
In addition, there is a case where a one-way clutch is disposed in an automatic transmission in parallel with a hydraulic friction element which is used as a transmission brake, and it is considered that the one-way clutch so disposed is constituted by the aforesaid plate type one-way clutch. FIGS. 6A, 6B show a hydraulic friction element with a one-way clutch of this type. In this one-way clutch, the first plate a and the second plate b of the one-way clutch are brought into spline engagement with an inner member c and an outer member d of the hydraulic friction element, respectively and are disposed so as to face each other in an axial direction thereof. Thus, when the first plate a rotates in a counterclockwise direction as shown in FIG. 6B, relatively to the second plate b, the pawls f mounted in the pocket portions e in the first plate a are allowed to sink into the pocket portions e to thereby permit the first plate a to rotate in the counterclockwise direction relatively to the second plate b, whereas the relative rotation of the first plate a to the second plate b in a clockwise direction is prevented by engagement of the pawls f with the notched portions g in the second plate b.
Here, a hinge portion f1 which is made wider than the other portions of the pawl f is formed at a proximal end of the pawl f which constitutes a forward portion of the pawl f when the first plate rotates in the counterclockwise direction, and a hinge receiving portion e1 which is wider than the other portions of the pocket portion e is formed in the pocket portion e at an end portion which constitutes a forward portion of the pocket portion e when the first plate rotates in the counterclockwise direction, so that the hinge portion f1 is brought into engagement with the hinge receiving portion e1. Accordingly, the pawl f is prevented from being dislocated from the pocket portion e in the clockwise direction when the first plate a rotates in the counterclockwise direction relatively to the second plate b.
With the aforesaid one-way clutch, when the outside diameter of the hydraulic friction element is reduced for miniaturization, the outside diameter of the first plate a is also reduced, and consequently the pocket portions e need to be formed in such a phase that the hinge receiving portions e1 in the pocket portions e coincide with tooth top portions a1 formed on an inner circumference of the first plate a for spline engagement with the inner member c. Here, the hinge receiving portions e1 are portions where restraining torque for preventing the relative rotation of the first plate a to the second plate b in the clockwise direction is inputted via pawls f. Therefore, if the pocket portions e are constructed as described above, sufficient strength cannot be obtained at the portions where the restraining torque is inputted and this facilitates the generation of cracks, the durability being thereby deteriorated.
The invention was made in view of the above situation, and an object thereof is to provide a plate type one-way clutch which has superior durability.
With a view to solving the problem, according to a first aspect of the invention, there is provided a one-way clutch comprising a pair of first and second plates facing each other in an axial direction thereof, wherein pocket portions are concavely provided in an axially internal surface of the first plate, while notched portions are concavely provided in an axially internal surface of the second plate, and wherein pawls are tiltably mounted in the pocket portions, whereby when the first plate rotates in one direction relative to the second plate the pawls are allowed to sink into the pocket portions to thereby permit the first plate to rotate in the one direction relative to the second plate, whereas the relative rotation of the first plate to the second plate in the other direction is prevented by engagement of the pawls with the notched portions, the one-way clutch being characterized in that the first plate is formed integrally with a rotating member for transmitting power to the first plate.
According to a second aspect of the invention, there is provided a one-way clutch adapted to be disposed in parallel with a hydraulic friction element and comprising a first plate adapted to connect to an inner member of the hydraulic friction element and a second plate disposed so as to face the first plate in an axial direction thereof and adapted to connect to an outer member of the hydraulic friction element, wherein pocket portions are concavely provided in an axially internal surface of the first plate, while notched portions are concavely provided in an axially internal surface of the second plate, and wherein pawls are tiltably mounted in the pocket portions, whereby when the first plate rotates in one direction relative to the second plate the pawls are allowed to sink into the pocket portions to thereby permit the first plate to rotate in the one direction relative to the second plate, whereas the relative rotation of the first plate to the second plate in the other direction is prevented by engagement of the pawls with the notched portions, the one-way clutch being characterized in that the first plate is formed integrally with the inner member of the hydraulic friction element.
According to the invention, the strength of the portions of the first plate where restraining torque is inputted via the pawls is reinforced by the rotating member (the inner member in the second aspect) made integral with the first plate to thereby prevent the generation of cracks, whereby the durability is improved.